A general methodology for the assessment of the impact of climate change - Evaluation of snow loads

Structural design of buildings and infrastructures is significantly influenced by the definition of climatic actions (snow, wind and thermal loads) that the structure shall withstand during its life, which could be significantly greater than the design service life. Therefore, the impact of climate change on climatic actions could significantly affect, in the mid-term future, the design of new structures as well as the reliability of existing ones designed in accordance to the provisions of present and past codes, which are based on the assumption of stationary climate conditions. In this work, a general methodology to derive future trends of snow load on structures is presented aiming to study the influence of climate change at European scale in view of the definition of updated snow maps for the new generation of structural Eurocodes. First, a general algorithm based, on Monte Carlo simulations, is defined to estimate ground snow loads maxima considering daily outputs of the climate models, in terms of maximum and minimum air temperatures and precipitation, supplemented by local information of snowfall and snow melting conditions derived from the elaboration of real measurements of actual meteorological events. Once validated the procedure, reproducing observed data series of yearly maximum ground snow loads, future trends in characteristic values of the load are investigated. Analysing different climate models and scenarios, the relevant issue of uncertainty assessment of climate projections is deeply investigated. In particular, the three main sources of uncertainty affecting climate projections: model uncertainty, scenarios uncertainty and internal variability, are assessed also implementing an innovative ad hoc developed weather generator, able to generate future weather series directly from climate model outputs. Factor of change confidence maps are finally derived combining all the presented results and providing guidance for potential amendments of the current version of snow load maps given in structural Codes.